JP4522973B2 - Method and apparatus for calculating thermal displacement of lead screw in feeder - Google Patents

Description

  The present invention relates to a method for calculating a thermal displacement amount of a feed screw in a feed device of a spindle device of a machine tool, for example, and an apparatus therefor.

  In a machine tool, a forward / backward movement saddle is mounted on a bed via a longitudinal guide rail, and a lateral movement saddle is attached to the forward / backward movement saddle via a lateral guide rail. Is mounted with a lifting saddle via a vertical guide rail, and a spindle device for gripping a tool is mounted on the lifting saddle. Each saddle is reciprocated by a feed device including a feed screw that is rotated forward and backward by a servo motor at a predetermined position and a nut that is screwed to the screw and attached to each saddle. . Then, each of the feeding devices is operated based on profile data programmed in advance in the control device, and the tool mounted on the spindle device is numerically controlled from the initial coordinates to process the workpiece. .

  The initial coordinates of the spindle device described above change as the feed screw of the feed device expands due to thermal expansion. For this reason, in order to prevent a reduction in workpiece machining accuracy, it is necessary to detect the amount of thermal displacement of the feed screw and correct the initial coordinates of the spindle device. In order to cope with this, in Patent Document 1, a position sensor is provided at a predetermined position of the column, and on the other hand, it is attached to the lower surface of the spindle head and is screwed to a feed screw shaft (feed screw). A magnet is attached to the outer periphery of the shaft, the position of the magnet is detected by the position sensor, the reference thermal displacement amount of the feed screw shaft at the reference position is detected, and the feed amount of the spindle head is corrected based on this. It has become.

Further, in Patent Document 2, a detector for measuring a change in the length of the screw is disposed opposite to the tip surface or the outer peripheral surface of the feed screw, and the movable screw can be moved based on the value measured by the detector. The body feed amount is corrected.
JP-A-6-15548 JP 2001-138178 A

  However, the method for correcting the amount of thermal displacement of the feed screw shaft in Patent Document 1 requires that a magnet be attached to the outer periphery of the female screw member, which increases the number of parts, complicates the structure, and makes the manufacturing and assembly work cumbersome. There was a problem that the cost could not be reduced. Further, when dust adheres to the magnet, there is a problem that the measurement accuracy of the thermal displacement amount is lowered.

  On the other hand, the thermal displacement correction device for a feed screw disclosed in Patent Document 2 has a configuration in which a detector is disposed at a position corresponding to the distal end surface of the feed screw or the outer peripheral surface of the distal end of the feed screw. There was a problem that the length dimension in the direction was increased.

  Also, the tip of the lead screw is supported rotatably and cannot move in the axial direction, and the base end of the feed screw on the servo motor side that rotates the feed screw is supported so that it can rotate and move in the axial direction. There was a problem that it could not be applied to the feeding device.

  The object of the present invention is to eliminate the above-mentioned problems in the prior art, reduce the number of parts, reduce the cost, improve the measurement accuracy of the thermal displacement amount, An object of the present invention is to provide a method for calculating the amount of thermal displacement of a feed screw in a feed device that can improve the degree of freedom of the mounting position, and the device.

In order to solve the above problems, the invention according to claim 1 is a feed in which one end of a feed screw is supported by a bearing so as not to move in the axial direction, and the other end is supported by a bearing so as to be movable in the axial direction. In the apparatus, of the both ends of the spiral groove formed in the feed screw , the feed screw is opposed to the end of the bearing-side spiral groove that supports the axial movement, and is orthogonal to the axial direction. from the fluid ejection nozzle provided so as to be toward the front Kinishi旋溝, with ejects fluid, by rotating the feed screw, to detect the pressure of the fluid, the amount of rotation of the feed screw, is detected Based on the measured pressure, the axial coordinates of the lead screw are calculated, and based on the reference coordinates previously calculated and stored and the actual coordinates obtained by the new calculation, the heat of the lead screw is calculated. The gist is to calculate the amount of displacement.

According to a second aspect of the present invention, in the first aspect of the present invention, the pressure and fluid in a pressure drop state of the fluid when the feed screw is rotated and the jet of fluid is transferred from the outer peripheral surface of the feed screw to the groove portion of the spiral groove. After calculating the amount of rotation of the feed screw when the pressure of the fluid pressure rise state when the jet of the nozzle moves from the groove portion of the spiral groove to the outer peripheral surface becomes a preset threshold value as the first coordinate and the second coordinate , The coordinate in the axial direction of the lead screw is calculated from the intermediate value of the two coordinates, and based on the reference coordinates previously calculated and stored and the actual coordinates newly obtained, The gist is to calculate the amount of thermal displacement.
According to a third aspect of the present invention, in the first aspect, when the feed screw is rotated and the fluid jet transitions from the outer peripheral surface of the feed screw to the spiral groove, the pressure in the fluid pressure drop state and the fluid jet The amount of rotation of the lead screw when one of the pressures in the fluid pressure rise state when moving from the spiral groove to the outer peripheral surface becomes a preset threshold value is calculated as a reference coordinate. The gist is to calculate the amount of thermal displacement of the lead screw on the basis of these coordinates and the actual coordinates newly calculated.

According to a fourth aspect of the present invention, in the feed device in which one end portion of the feed screw is supported by the bearing so as not to move in the axial direction, and the other end portion is supported by the bearing so as to be movable in the axial direction, the both bearings are supported. The frame is opposed to the end of the spiral groove on the bearing side that supports the feed screw so as to be movable in the axial direction, and is orthogonal to the axial direction, at both ends of the spiral groove of the feed screw. provided a fluid injection nozzle for injecting toward the front Kinishi旋溝during rotation of the fluid from the pressure fluid supply source, a pressure detecting means for detecting the pressure of the fluid ejected from the fluid ejection nozzle, said feed screw A rotation amount detecting means for detecting the rotation amount of the lead screw, a coordinate for calculating the coordinate in the axial direction of the feed screw based on the pressure detected by the pressure detection means and the rotation amount detected by the rotation amount detection means Computing means and above Thermal displacement amount for calculating the thermal displacement amount of the lead screw based on the reference coordinates previously calculated and stored by the standard calculation means and the actual coordinates newly calculated by the coordinate calculation means The gist of the present invention is to provide a calculation means.

According to a fifth aspect of the present invention, in the fourth aspect , the coordinate calculation means is configured such that the pressure of the fluid when the feed screw is rotated and the injection of the fluid is transferred from the outer peripheral surface of the feed screw to the groove portion of the spiral groove. The amount of rotation of the feed screw when the pressure in the lowered state and the pressure of the fluid in the fluid pressure rising state when the fluid injection moves from the groove portion of the spiral groove to the outer peripheral surface becomes a preset threshold value and the first coordinate The gist is that, after calculating as two coordinates, the coordinate in the axial direction of the feed screw is calculated from the intermediate value of both coordinates.
According to a sixth aspect of the present invention, in the fourth aspect of the present invention, the coordinate calculation means is configured such that the pressure drop state of the fluid when the feed screw is rotated and the fluid injection is transferred from the outer peripheral surface of the feed screw to the spiral groove. The amount of rotation of the feed screw when the pressure of one of the pressure of the fluid and the pressure of the fluid pressure rise state when the fluid injection moves from the spiral groove to the outer peripheral surface becomes a preset threshold value as a reference coordinate The gist is that it is configured to calculate.

  According to the present invention, the coordinate in the axial direction of the feed screw is calculated based on the rotation amount of the feed screw and the detected pressure, and a new calculation is made with the reference coordinate previously calculated and stored. Since the amount of thermal displacement of the lead screw is calculated based on the actual coordinates obtained in this way, it is not necessary to provide an object to be measured on the lead screw, and the number of parts can be reduced and the cost can be reduced.

  Further, since the fluid is ejected to the feed screw, the outer peripheral surface of the screw is cleaned, the measurement accuracy of the thermal displacement amount can be improved, and the degree of freedom of the mounting position of the fluid ejection nozzle can be improved.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment in which the invention is embodied in a feed screw feeding device of a machine tool will be described with reference to the drawings.
As shown in FIG. 1, a pair of bearing bases 12 and 13 are erected on a top surface of a base (frame) 11 of a machine tool at a predetermined interval, and both bearing bases 12 and 13 have bearings (bearings) 14. , 15, the feed screw 16 is rotatably supported. A spiral groove 16b is formed on the outer peripheral surface 16a of the feed screw 16 except for both ends, and a stopper 17 is fitted and fixed to the outer peripheral surface of the base end portion 16c of the feed screw 16, and the feed screw 16 is It is supported so that it cannot move in the axial direction. A distal end portion 16 d of the feed screw 16 is supported by the bearing 15 so as to be movable in the axial direction.

  A servo motor 19 is attached to the upper surface of the base 11 via a bracket 18, and a rotating shaft 19 a and the base end portion 16 c of the servo motor 19 are connected by a joint 20. The servo motor 19 is provided with an encoder 21 as rotation amount detecting means for detecting the rotation amount of the rotating shaft 19a.

  An air injection nozzle as a fluid injection nozzle is provided on the upper surface of the base 11 via a bracket 24 so as to face one end of the spiral groove 16b of the feed screw 16 near the tip end portion 16d. 25 is erected. The distance L between the front end surface of the air injection nozzle 25 and the outer peripheral surface 16a of the feed screw 16 is set to 0.5 to 1.0 mm, for example. Air is supplied to the air injection nozzle 25 through a pipe 27 and an on-off valve 28 from a compressor 26 as a pressure fluid supply source. A pressure detector 29 is connected to the pipe 27 as pressure detecting means for detecting the pressure of air injected from the air injection nozzle 25 toward the outer peripheral surface of the feed screw 16.

Next, the control system for the feeder configured as described above will be described with reference to FIG.
The control device 31 is provided with a central processing unit (CPU) 32 for performing various arithmetic processes. The CPU 32 is connected to a read only memory (ROM) 33 as a rewritable nonvolatile storage medium storing various data such as a machining program for controlling the operation of the machine tool or a measurement program. . The CPU 32 is connected to a random access memory (RAM) 34 as a readable / writable storage medium for storing various data. The CPU 32 is connected to the pressure detector 29 and the encoder 21 via an input / output interface 35 and an A / D converter (not shown). Similarly, the servo motor 19, the compressor 26 and the on-off valve 28 are connected to the CPU 32 via an input / output interface 36 and a drive circuit 37.

Furthermore, a display unit 39 and an operation input unit 40 such as a keyboard or a mouse are connected to the CPU 32 via an input / output interface 38.
The CPU 32 calculates an axial coordinate Zx of the spiral groove 16b of the feed screw 16 based on the rotation amount θx of the feed screw 16 detected by the encoder 21 and the pressure Px detected by the pressure detector 29. A coordinate calculation unit 41 is provided as coordinate calculation means. The random access memory 34 is provided with a threshold value storage unit 42 for storing a pressure threshold value, and for storing the reference coordinate Zk of the spiral groove 16b of the feed screw 16 calculated by the coordinate calculation unit 41. A reference coordinate storage unit 43 and an actual coordinate storage unit 44 for storing newly calculated actual coordinates Zg are provided. The central processing unit 32 includes a movement for correcting the movement command value (initial coordinates) of the movable body 22 based on the reference coordinate Zk of the spiral groove 16b of the feed screw 16 and the actual coordinate Zg. A command value correction calculation unit 45 is provided.

  Next, the operation of the CPU 32 of the control device 31 configured as described above and the operation of the feeding device performed by various signals output from the control device 31 will be described with reference to FIG.

  In the state where the feed screw 16 is stopped at the origin position, as shown in FIG. 3, the circumferential center portion of the outer peripheral surface 16 a of the feed screw 16 corresponds to the injection port 25 a at the tip of the air injection nozzle 25, and The rotation amount θ signal output from the encoder 21 is set to 0 °.

  In this state, when air is injected from the air injection nozzle 25 toward the outer peripheral surface 16 a of the feed screw 16, the pressure of the air is detected by the pressure detector 29, and the detected pressure Ps is input to the control device 31. In synchronization with this, when a start signal is output from the control device 31 to the servomotor 19 and the feed screw 16 is rotated at a low speed, the groove portion leading side with respect to the rotation direction of the outer peripheral surface 16a of the feed screw 16 and the spiral groove 16b. The first edge portion 16e approaches the air injection nozzle 25, so that the air also enters the groove portion of the spiral groove 16b and the air injection resistance is reduced, so that a pressure drop starts as shown by a curve in FIG. . When the first edge portion 16e is completely separated from the air injection nozzle 25 and only the groove portion of the spiral groove 16b corresponds to the air injection nozzle 25, the detected pressure Ps becomes the lowest. Thereafter, when the second edge portion 16f on the rear side of the groove portion in the rotational direction of the spiral groove 16b of the feed screw 16 approaches the air injection nozzle 25, the air injection resistance increases, and thus the pressure starts to increase. Further, when the second edge portion 16f is completely separated from the air injection nozzle 25 and only the outer peripheral surface 16a corresponds to the air injection nozzle 25, the detected pressure Ps becomes maximum.

  In FIG. 3, the rotation amount θ1 of the first edge portion 16e when the detected pressure Ps reaches the threshold value Pc is calculated by the coordinate calculation unit 41, and this is set as the first edge coordinate Z1 in the Z-axis direction of the first edge portion 16e. Stored in the RAM 34. Similarly, the rotation amount θ2 of the second edge portion 16f when the detected pressure Ps becomes the threshold value Pc is calculated by the coordinate calculation unit 41, and this is set as the second edge coordinate Z2 of the second edge portion 16f in the Z-axis direction. Stored in the RAM 34. Further, based on the first edge coordinate Z1 and the second edge coordinate Z2, the coordinate calculation unit 41 calculates the coordinate of the center point in the circumferential direction of the groove portion of the spiral groove 16b from the intermediate value of the two coordinates, and this is the reference. Is stored in the reference coordinate storage unit 43 as the coordinate Zk.

  As described above, after the reference coordinate Zk of the center point in the circumferential direction of the groove portion of the spiral groove 16b of the feed screw 16 is stored, the servo motor 19 is rotated to move the movable body 22 in the axial direction of the feed screw 16. When reciprocating, the feed screw 16 is heated and thermally expanded due to frictional resistance between the spiral groove 16b and the ball on the nut 23 side or heat generated by the motor. Due to the thermal expansion of the feed screw 16, the coordinates of the center point of the groove portion of the spiral groove 16b also change. For this reason, the detected pressure Ps changes as shown by a two-dot chain line in FIG. 3, and based on this, the actual first edge coordinate Z1 ′, the second edge coordinate Z2 ′, and the spiral groove 16b are detected by the coordinate calculation unit 41. The actual coordinate Zg of the center point is calculated and stored in the actual coordinate storage unit 44. Then, based on the reference coordinate Zk and the actual coordinate Zg, the movement command value correction calculation unit 45 calculates a coordinate error ΔZ (= Zk−Zg). Based on the coordinate error ΔZ, the movement command value (initial coordinate) ) Is corrected. As a result, the amount of movement of the movable body 22 is appropriately corrected, and the workpiece machining accuracy can be improved.

According to the thermal displacement calculation device for the feed screw in the feed device of the above embodiment, the following effects can be obtained.
(1) In the above embodiment, the air injection nozzle 25 is disposed at a position corresponding to the spiral groove 16b of the feed screw 16, and the detected pressure Ps of the air injected by rotating the feed screw 16 and the detection of the feed screw 16 are detected. The reference coordinate Zk of the circumferential center point of the spiral groove 16b of the feed screw 16 is calculated based on the rotation amount θ, and the thermal displacement amount of the feed screw 16 is calculated based on this and the actual coordinate Zg. I made it. For this reason, it is not necessary to attach a measurement-dedicated part to the lead screw 16 to be measured, the number of parts can be reduced, manufacturing can be facilitated, and cost can be reduced.

  (2) In the above embodiment, since air is jetted from the air jet nozzle 25 to the feed screw 16, dust adhering to the feed screw 16 can be removed and the measurement accuracy of the thermal displacement amount can be improved. .

  (3) In the above embodiment, since the air injection nozzle 25 is disposed at a position corresponding to the spiral groove 16b of the feed screw 16, a conventional configuration in which a detector is provided corresponding to the tip surface of the feed screw 16; In comparison, the degree of freedom of the mounting position of the air injection nozzle 25 can be improved. In addition, the air injection nozzle 25 can be easily applied to a feeding device having a configuration in which the distal end portion 16d of the feed screw 16 is not movable in the axial direction and the proximal end portion 16c is movable. Therefore, the degree of freedom of the mounting position of the air injection nozzle 25 can be improved.

In addition, you may change the said embodiment as follows.
In FIG. 3, when the feed screw 16 is rotated and the air injection shifts from the outer peripheral surface 16a of the feed screw 16 to the groove portion of the spiral groove 16b, the detected pressure Ps of the fluid pressure drop state and the air injection are performed. Based on either the rotation amount θ1 or θ2 of the feed screw 16 when the detected pressure Ps of the fluid pressure rise state when moving from the groove portion of the spiral groove 16b to the outer peripheral surface 16a becomes a preset threshold value Pc. Is calculated as the coordinate Zk. Then, the thermal displacement amount of the lead screw may be calculated on the basis of the reference coordinate Zk and the actual coordinate newly calculated in the same manner as this calculation method.

-Instead of air, liquids such as coolant may be jetted .

The longitudinal cross-sectional view which shows one Embodiment which actualized this invention to the feeder of a machine tool. The block circuit diagram which shows the control system of a feeder. The timing chart for demonstrating operation | movement of a feeder.

Explanation of symbols

  Pc ... threshold, Zg ... actual coordinates, Zk ... reference coordinates, 16 ... feed screw, 16a ... outer peripheral surface, 16b ... spiral groove.

Claims (6)

In a feed device in which one end of the feed screw is supported by a bearing so as not to move in the axial direction, and the other end is supported by a bearing so as to be movable in the axial direction.
Out of the both ends of the spiral groove formed in the feed screw , the feed screw is opposed to the end of the spiral groove on the bearing side that supports the axial movement so as to be orthogonal to the axial direction. toward the front Kinishi旋溝from a fluid ejection nozzle provided, as well as injecting a fluid, said feed screw is rotated, detects the pressure of the fluid, the amount of rotation of the feed screw, and the detected pressure Based on the above, the coordinate in the axial direction of the lead screw is calculated, and the thermal displacement amount of the lead screw is calculated on the basis of the reference coordinate previously calculated and stored and the actual coordinate newly obtained. A method for calculating a thermal displacement amount of a feed screw in a feed device, characterized by: 2. The pressure in the pressure drop state of the fluid and the jet of the fluid from the outer periphery of the feed screw to the outer periphery of the spiral groove when the feed screw is rotated to the outer periphery of the spiral groove from the outer periphery of the spiral groove. After calculating the rotation amount of the feed screw when the pressure in the fluid pressure rising state when moving to the surface becomes a preset threshold value as the first coordinate and the second coordinate, the feed from the intermediate value of both coordinates Calculates the axial displacement of the screw and calculates the amount of thermal displacement of the lead screw based on the previously calculated and stored reference coordinates and the actual coordinates newly calculated. A method for calculating the amount of thermal displacement of the feed screw in the feed device. 2. The pressure in the pressure drop state of the fluid and the fluid ejection are transferred from the spiral groove to the outer peripheral surface when the feed screw is rotated and the fluid injection is transferred from the outer peripheral surface of the feed screw to the spiral groove. The amount of rotation of the lead screw when either one of the pressures in the fluid pressure rise state becomes a preset threshold value is calculated as a reference coordinate, and this reference coordinate is newly calculated. A thermal displacement amount calculation method for a feed screw in a feed device, wherein the thermal displacement amount of the feed screw is calculated based on the actual coordinates obtained. In a feed device in which one end of the feed screw is supported by a bearing so as not to move in the axial direction, and the other end is supported by a bearing so as to be movable in the axial direction.
The frame that supports both the bearings is opposed to the end of the spiral groove on the bearing side that supports the feed screw so as to be movable in the axial direction among both ends of the spiral groove of the feed screw , and the shaft provided so as to be orthogonal to the direction, and a fluid injection nozzle for injecting toward the front Kinishi旋溝during rotation of the fluid from the pressure fluid supply source,
Pressure detection means for detecting the pressure of fluid ejected from the fluid ejection nozzle;
A rotation amount detecting means for detecting a rotation amount of the feed screw;
Coordinate calculation means for calculating the axial coordinate of the lead screw based on the pressure detected by the pressure detection means and the rotation amount detected by the rotation amount detection means;
Thermal displacement for calculating the amount of thermal displacement of the lead screw based on the reference coordinates previously calculated and stored by the coordinate calculation means and the actual coordinates newly calculated by the coordinate calculation means A heat displacement amount calculation device for a feed screw in a feed device, comprising: an amount calculation means. 5. The coordinate calculation means according to claim 4 , wherein the coordinate calculation means is configured to perform pressure drop and fluid injection in a fluid pressure drop state when the feed screw is rotated and fluid injection is transferred from the outer peripheral surface of the feed screw to the groove portion of the spiral groove. After calculating the rotation amount of the lead screw when the pressure in the fluid pressure rising state when moving from the groove portion of the spiral groove to the outer peripheral surface becomes a preset threshold value as the first coordinate and the second coordinate, both coordinates An apparatus for calculating a thermal displacement amount of a feed screw in a feed device, wherein the coordinate in the axial direction of the feed screw is calculated from an intermediate value of the feed screw. 5. The coordinate calculation means according to claim 4, wherein the coordinate calculation means is configured so that the pressure in the pressure drop state of the fluid and the fluid ejection are spiral grooves when the feed screw is rotated and the fluid ejection transitions from the outer peripheral surface of the feed screw to the spiral groove. The amount of rotation of the lead screw when the pressure of one of the fluid pressure rising pressures when moving from the outer surface to the outer peripheral surface becomes a preset threshold value is calculated as a reference coordinate An apparatus for calculating a thermal displacement amount of a feed screw in a feed device characterized by the above.

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